Imaging devices, such as consumer digital still cameras, video cameras, and built-in cameras of mobile phones, provide increasingly high functionality nowadays. These high-functionality imaging devices have functions of taking high-quality pictures or videos, as well as sophisticated functions such as rapid continuous shooting, or functions of automatically assigning meta-information, such as location information on the location of shooting or information on the name of a person in a photograph or video, for example. Such imaging devices having diverse functions are now available to users at low costs.
Popularity of these high-functionality imaging devices is a factor to increase private content handled by individuals, for example, photographs of a family trip or an athletic meet, a video of a recital, etc. With improvement in image quality or increase in added value of content, the size of individual content items is exploding in addition to increase in the amount of data handled by individuals.
There are also increasing occasions where albums or business documents for printing are created with such pictures and the like. In general, images embedded in an album or document increase file size. To address this, an approach is proposed that detects features of such an embedded image using color components of the image and the number and size of face regions, and compresses the image by a predetermined factor when the image is determined to be a photograph image from its color components (see PTL 1, for instance).